The present invention relates to electric power plants and more particularly to systems which employ gas turbines to make black starts for large fossil fired electric power plants.
A black fossil plant startup is one which is made when the plant has become isolated from the surrounding electric power system and thus must bootstrap itself into an operating state. The degree of difficulty in making a black start depends on the size of the plant and the power needed to drive all of the auxiliary equipment which must be operating before the plant can start generating electric power.
One way in which black plant starts can be achieved is through the use of a small boiler which when fired generates enough steam to drive steam operated auxiliary pumps and other equipment associated with a larger boiler. Once the larger boiler is started and supplies steam to a turbine-generator unit, electric power is generated for use in operating electric powered auxiliaries associated with other boilers located at the plant site.
Gas turbine-generator units have not been known to have been used commercially to make black plant starts for large fossil fired electric power plants, although the possibility of a black plant startup system employing a gas turbine generator has been considered from time to time. One of the principal difficulties in realizing a gas turbine black plant startup system has been the loading problems created by the larger plant auxiliary electric motors, such as 7000 HP forced draft or induced draft fan motors. Such motors and other electric auxiliaries create dead loading for a gas turbine during the fossil plant black startup and unless properly handled by the startup system can produce excessive stress damage to gas turbines rated at 30 MW or even higher.
Gas turbines have been operated for dead load pickup, for example as set forth in copending and coassigned patent application Ser. No. 703,737, entitled "System For Operating Multiple Gas Turbines For Coordinated Dead Load Pickup" filed by R. A. Yannone et al. on Apr. 9, 1976. However, that application and other known prior art have no direct bearing on the special problem of black steam plant starts.